Field of the Invention
The present invention relates to an information recording/reproducing apparatus for reading or writing the information, employing an optical information recording/reproducing medium such as a CD (Compact Disk) or a DVD (Digital Video Disk or Digital Versatile Disk).
The conventional information recording/reproducing apparatus for reading or writing the information employing the optical information recording/reproducing medium (hereinafter referred to as an xe2x80x9coptical diskxe2x80x9d) such as CD or DVD comprises a pickup 2 having an objective lens 1 for directing a light beam onto the optical disk, and a movement mechanism for moving the pickup 2 in a radial direction of the optical disk, as shown in FIG. 10.
The movement mechanism comprises two guide shafts 3, 4 and a lead screw 5 which are disposed in parallel along the radial direction of the optical disk, and a driving motor 8 for rotating the lead screw 5, in which the pickup 2 is supported in freely slidable manner by the two guide shafts 3, 4, and can be moved by shifting the engaging positions of the projections 6, 7 formed at one end of the pickup 2 with the lead screw 5.
That is, if the lead screw 5 is rotated in a predetermined direction under a driving force of the driving motor 8, the engaged positions of the projections 6, 7 with the tooth flank of the lead screw 5 are displaced toward the outer circumferential side of the optical disk in accordance with the amount of rotation. Also, if the lead screw 5 is rotated in a reverse direction under a driving force of the driving motor 8, the engaging positions of the projections 6, 7 with the tooth flank of the lead screw 5 are displaced toward the inner circumferential side of the optical disk in accordance with the amount of reverse rotation. Along with the displacement of the projections 6, 7, the pickup 2 is moved toward the inner circumferential side or the outer circumferential side, so that the pickup 2 can gain access to the position for reading or writing the information of the optical disk randomly.
Also, a detection switch 9 or 10 for detecting a home position (reference position) of the pickup 2 is provided on one side of the guide shafts 3, 4 in a longitudinal direction (i.e., guide direction). It is common practice that the home position is detected by the detection switch 9 provided on the inner circumferential side of the optical disk.
And the pickup 2 is forcefully moved toward the inner circumferential side to press the detection switch 9, so that a detection signal is output from the detection switch 9. On the basis of this detection signal, the home position of the pickup 2 is detected. Further, if the maximum number of driving pulses to be supplied to the driving motor 8 is predetermined with reference to the home position, the movable range of the pickup 2 can be set up.
Also, when the detection switch 10 is provided on the outer circumferential side of the optical disk, the pickup 2 is moved forcefully toward the outer circumferential side to press the detection switch 10, so that a detection signal is output from the detection switch 10. On the basis of this detection signal, the home position of the pickup 2 is detected. Further, if the maximum number of driving pulses to be supplied to the driving motor 8 is predetermined with reference to the home position, the movable range of the pickup 2 can be set up.
By the way, in the conventional information recording/reproducing apparatus as described above, it is required to have the detection switch 9 (or 10) to detect the home position of the pickup 2, resulting in the problem that the number of parts is increased.
To avoid an increase in the number of parts, instead of the detection switch 9 (or 10), a movement regulation member with simple structure such as a projection may be provided at the home position, whereby the pickup 2 is forcefully pressed and stopped against the movement regulation member by driving the driving motor 8 beyond the movable range, and moved to the home position.
However, with such a constitution, when the pickup 2 is moved to the home position, the lead screw 5 continues to be rotated under a driving force of the driving motor 8, although the pickup 2 is brought into direct contact with the movement regulation member and is unmovable. Consequently, the projections 6, 7 get rid of the tooth flank of the lead screw 5, resulting in the problem that there occurs a harsh sound between the projections 6, 7 and the tooth flank.
That is, a phenomenon that the projections 6, 7 get rid of the tooth flank of the lead screw 5 is called a xe2x80x9cout of toothxe2x80x9d. If this out of tooth occurs, there occurs a harsh large sound such as a xe2x80x9cscratching soundxe2x80x9d or a xe2x80x9ccracking soundxe2x80x9d, when the projections 6, 7 ride over a crest of the tooth flank of the lead screw 5, and fall in an adjacent trough again, thereby causing the problem that the user may be discomforted.
The present invention has been achieved to overcome the above-mentioned problems associated with the prior art, and it is an object of the invention to provide an information recording/reproducing apparatus that allows a pickup to gain fast access to an information recording/reproducing medium.
To accomplish the above object, according to the present invention, there is provided an information recording/reproducing apparatus for reading or writing the information by moving a pickup within a predetermined movement range over an information recording/reproducing medium, comprising a lead screw extending in a predetermined direction with respect to the information recording/reproducing medium, driving means for driving the lead screw in rotation, support means for supporting the pickup movably along an extending direction of the lead screw, engaging members for engaging with a tooth flank of the lead screw and integrated with the pickup, regulation means for regulating a movable range of the pickup, and control means for controlling the driving means to drive the lead screw in rotation to bring the pickup into direct contact with the regulation means to normalize a reference position of the pickup in the movable range, wherein the tooth flank of the lead screw engaged by the engaging members is formed like a shape causing a step out when the pickup comes into direct contact with the regulation means.
The regulation means is provided at a position off a loading position of the information recording/reproducing medium.
With the above constitution, the operation for normalizing the reference position of the pickup is performed by bringing the pickup into direct contact with the regulation means. If the pickup is brought into direct contact with the regulation means, a phenomenon of xe2x80x9cstep outxe2x80x9d occurs between the engaging members and the tooth flank of lead screw. If this phenomenon of xe2x80x9cstep outxe2x80x9d occurs, the engaging members engage strongly with the trough of the tooth flank of lead screw and are stopped, and the driving means is stopped under a load exerted. Namely, this phenomenon, unlike the phenomenon in which the engaging members get rid of the tooth flank of lead screw, like xe2x80x9cout of toothxe2x80x9d, is such that the engaging members engage strongly with the trough of the tooth flank of lead screw and are stopped. Therefore, the occurrence of imitation sound such as xe2x80x9cout of toothxe2x80x9d is suppressed, enabling the silence of the apparatus itself.
Also, the control means controls the driving means to rotate the lead screw to bring the pickup into direct contact with the regulation means, and then the driving means to rotate the lead screw by a predetermined amount to move the pickup to a position off the regulation means and to normalize the position after movement as the reference position of the pickup.
With the above constitution, the position near the management information recording area provided on the side of the loading position of the information recording/reproducing medium is set up as the reference position of the pickup, and the pickup can gain access to the management information recording area to make promptly the information reading or writing operation.
Also, the regulation means is provided near the loading position of the information recording/reproducing medium, and the control means controls the driving means to drive the lead screw in rotation to bring the pickup into direct contact with the regulation means at a position near the loading position of the information recording/reproducing medium to normalize the reference position of the pickup in the movable range.
With such a constitution, only by making one normalization, the position near the management information recording area provided on the side of the loading position of the information recording/reproducing medium is set up as the reference position of the pickup, and the pickup can gain access to the management information recording area to make promptly the information reading or writing operation.